The project is designed to develop new instrumentation and methodolgy or improve existing instrumentation and methodology for characterization of biological macromolecules. Analytical ultracentrifugation, the techniques ancillary to it, and methods of data analysis using mathematical modeling appropriate for these techniques are the major areas of interest. Improved precision and optimal efficiency in ultracentrifugal analysis requires improved methods of data acquisition. A microprocessor controlled data acquisition instrument for use with the microcomparator used for the measurement of photographic records from the ultracentrifuge has been developed earlier. The methods of data acquisition involved in the development of this instrument have been extended to the development of a system for the direct acquisition of data from the photomultiplier tube of the ultraviolet absorption scanner of the ultracentrifuge. The software requisite for making this system operational is currently in development. When complete, this system will permit direct acquisition of data while the ultracentrifuge is operating and then permit preliminary data processing followed by transmission of the data to the DEC-10 computer for detailed analysis. This will effect a marked increase in efficiency, significantly improved precision, enhanced facility in data analysis and will also more readily permit the effective modification of some experimental conditions such as rotor speed and temperature during the course of the experiment if the analysis indicates it to be desirable. MLAB, operating on the DEC-10 computer, has been used for mathematical modeling studies for the analysis of various types of protein interactions. These studies have been applied to ultracentrifugal studies of binding and of protein self-association.